A vortex air nozzle is known for yarn spinning from staple fibers, comprising an inlet chamber for the formation of free tails of the fibers, the chamber being connected to tangential channels for compressed air supply. Close to an outlet pair of drafting rollers approximately intersecting the drawing line of the roving is placed a deflection roller. Part of the circumferential surface of that roller lies in the inlet chamber for the formation of fibers free tails (EP DO No. 57876).
A disadvantage of this nozzle is that because of the direct compressed air feeding in the outlet twisting chamber, the axial component is not sufficient to ensure a reliable transport of the roving and its reliable passage through the narrowed outlet of the inlet chamber in the formation of the fibers free tails. A vortex air nozzle (German patent document No. 32 46 146) is known for yarn spinning from staple fibers, which comprises an inlet chamber for fibers free tail formation and an outlet chamber for twisting. The wider part of that section is a parallel to the drawing line, and there are grooved channels in the chamber for avoiding the rotation of the roving when the false twist is imparted for the formation of the free tails. At its end, the inlet chamber takes a cylindrical form, and is connected to the outlet twisting chamber. The outlet chamber wall are formed with tangential channels for compressed air feed. The tangential channels are inclined toward the end of the inlet chamber. The above mentioned inlet and outlet chambers are formed as a common body of the vortex air nozzle, which is placed close to the outlet pair of drawing rollers.
The disadvantage of this nozzle is that the torque moment, imparted in the outlet twisting chamber is only partially delivered despite the abovementioned grooved channels. The twist possible at the infeed of the roving the inlet chamber for the formation for the formation of free tails makes the formation of the free tails of the fibers difficult. Another disadvantage of the said nozzle is that the compressed air is directly fed to the outgoing twisting chamber. The said air flux is inclined towards the movement of the fibrous ribbon, promoting the transport of the ribbon and its free movement through the narrow cylindrical part of the inlet chamber for the formation of free tails of fibers. But the axial component of the air flow is not sufficient to ensure a reliable transport of the roving, and the roving has fiber free tails.